An improvised explosive device (IED) is a weapon that is fabricated or emplaced in an unconventional manner incorporating destructive, lethal, noxious, pyrotechnic, and/or incendiary chemicals or other materials designed to kill, destroy, incapacitate, harass, deny mobility, and/or distract. IEDs vary widely in shape, size, and form; however, they usually share three components: main charge, container, and initiator or initiating system, e.g., detonator. An IED may also contain one or more enhancements, which is a component deliberately added to an IED as a secondary hazard to modify or enhance the effect(s) or end result(s) of the IED. An enhanced effect can be, for example, additional physical destruction, fragmentation, or proliferation of dangerous substances, e.g., chemical, biological, radiological, or nuclear (CBRN) hazards. IEDs can be initiated at the IED or electronically in a wireless method by employing a transmitter and receiver, e.g., personal mobile radio, cell phone, cordless phone, or pager. If initiation occurs electronically in a wireless method, then the IED is known as a radio-controlled IED (RCIED).
The main charge is the explosive charge provided to accomplish the end result in, for example, munitions. Examples of end results include, but are not limited to, bursting a casing to provide blast and fragmentation, splitting a canister to dispense submunitions, and producing other deleterious effects. The main charge constitutes the bulk explosive component of an IED and can be configured for directional effects. Explosives fall into two categories: low and high yield. Low yield explosives are combustible materials that deflagrate, do not produce a shock wave, and must be confined to explode, e.g., black powder. High yield explosives are materials that detonate with a shockwave and do not require confinement, e.g., dynamite.
The second common IED component is the container, which is a vessel often used to conceal an IED or parts of an IED to prevent discovery of the IED by visual inspection. Alternatively, the container can be a confinement container, which is a vessel commonly used to hold the main charge together. Some examples of containers are carcasses, pipes, backpacks, jugs, tires, briefcases, vests, and vehicles.
The third common IED component is the initiator or initiating system (also known as an energetic witness). Any component used to start a detonation or deflagration can function as an initiator or initiating system, such as an electric match or a detonator. All initiators or initiating systems have time, power, and energy requirements and fall into two categories: non-electric and electric.
A non-electric initiator uses a stimulus, such as heat, shock, friction, or impact, to cause the explosive material to ignite or detonate. Non-electric initiators are activated by non-electrical means, e.g., the mechanical energy from a recoiled spring can actuate a non-electric initiator to subsequently detonate a main charge. Electric initiators are activated by an electrical impulse that creates heat or a spark. Examples of initiators include, but are not limited to: (1) blasting cap or plain detonator, which is an electric or non-electric device containing a sensitive explosive intended to produce a detonation wave upon activation; (2) exploding bridgewire (EBW), which is an initiator wherein a very high-energy electrical impulse is passed through a bridgewire, literally exploding the bridgewire and releasing thermal and shock energy capable of initiating a relatively insensitive explosive in contact with the bridgewire; (3) heat initiator, which is an initiator that serves as an igniting element through the application of heat, including direct heat, to a sensitive explosive; (4) light/flash bulb initiator, which is a device used as an electric initiator that incorporates a bulb to activate primary or low explosives; (5) percussion initiator, which is an initiator that serves as an igniting element when mechanically struck; (6) shock tube, which is, generally, a thin, plastic tube of extruded polymer with a layer of high explosive deposited on its interior surface that propagates a detonation wave to a blasting cap; (7) squib/igniter, which is any chemical, electrical, or mechanical device used to ignite a combustible material, e.g., initiate low or high explosives in a firing train; and (8) time fuse/safety fuse, which is a pyrotechnic contained in, generally, a flexible and weatherproof sheath that burns at a timed and constant rate and transmits a flame to a detonator or a low explosive charge with a pre-determined delay.
A common example of an electric initiator is a hot-wire detonator, which has at least three components: header, bridgewire, and ignition charge. The bridgewire can be wire, filament, or other form, and is generally comprised of a metal, such as gold, platinum, tungsten, or chromium; an alloy, such as nichrome, platinum/iridium, gold/iridium, gold/rhodium, or platinum/rhodium; or another conducting material, e.g., semiconductor. The most common bridgewire material is fine gauge nichrome wire. The bridgewire generally has lead wires for electrical inputs, but it can also be placed directly into an electric connector.
The bridgewire produces heat when current is applied, which causes the explosive material to ignite or detonate. The base energetic material for many hot-wire detonators is a pyrotechnic mixture known as a pyrogen that requires heating to a particular minimum temperature to start a reaction. The heat generated by the bridgewire initiates detonation, because, when electric power is applied, heat is imparted to the pyrogenic mixture causing it to ignite and/or causing a small explosive charge to detonate. Alternatively, a detonator may contain a bridgewire that explosively vaporizes after application of a sudden surge of power. In many detonators, the energies required to bring a thermal bridgewire up to a sufficient initiation temperature (about 350° C.) is less than about 15 mJ with reliable firing when the power is greater than about 40 milliwatts.
In addition to the main charge, initiator or initiating system, and container, IEDs contain a power source, which stores or releases electrical or mechanical energy to initiate the IED's main charge. The most common power source found in an IED is a battery or batteries. Alternating current may also be used as the power source. The key elements of a power source are: type/source; number of components, e.g., batteries, and their configuration (series or parallel); voltage (if applicable); and how it is connected to close an IED switch, which is another component of an IED.
The switch is a device for making, breaking, or changing an electrical or non-electrical connection. Insurgents and terrorists often employ switches to arm or fire an IED. A single switch can have multiple functions, e.g., safe-to-arm and fire. Some bomb makers use safe-to-arm switches to reduce the risk of accidental detonation during IED emplacement. Electric IEDs are classified by their firing switches into three main categories: command switches, time switches, and victim-operated switches.
Currently, training aids used at training facilities for bomb technicians, such as the Hazardous Devices School in Alabama, do not use energetic witnesses and there is no effective substitute for an energetic witness. One reason for needing an effective energetic witness substitute is because it can function as an audible or visual witness in a training aid, thus avoiding the use of an actual energetic witness, which can be hazardous due to the potential for fire and bodily injury. In addition, in view of the potential hazards, the use of actual energetic witnesses limits venues available for training and testing. Another reason for the need for energetic witness substitutes is the fact that detonators and electric matches, for example, which are used in real IEDs, are fast responding devices, which is a consideration in render-safe procedures (RSP) used to disable or reduce the functionality of IEDs.
Energetic witness substitutes currently in use, e.g., buzzers, vibrators, indicator lights, and beepers, may indicate a switch was thrown in a training IED or other target device being tested, but they do not take into account the power and energy requirements or the time-to-function of a real IED, and thus cannot indicate whether the power, energy, and time thresholds needed for the IED to function have been reached. For example, a switch may be transiently triggered so that the slow response of indicator lights, beepers, or other responses go undetected. If a switch closes and then opens and the indicator (light or beeper, for example) is on for a very brief period of time, there may be no detectable response to the observer. If the indicator has a slow response time, it may never turn on due to a fast transient stimulus. In other cases, a light or beeper, for example, may have nominal power requirements to produce visible light or sound, respectively. If the IED output does not provide enough current to produce visible light or audible sound, respectively, it may appear as if nothing happened. It is possible to have continuous current or a current pulse flowing through an incandescent bulb, for example, yet no light is detected. However, an actual IED will consistently function after receiving the same stimulus. Moreover, certain lights and beepers designed for low power devices, such as light emitting diodes (LEDs), piezo beepers, and buzzers, may activate, despite the detonator power and energy thresholds not having been met.
In addition to buzzers, beepers, vibrators, and indicator lights being poor indicators of IED switching and functionality, they are also inadequate for determining whether an IED would function during an RSP. A completely rendered safe device has all its functional components separated and placed in an environment that minimizes any hazard they present. Currently, no method exists that employs a non-explosive component to effectively duplicate the performance of a detonator in a mock IED or in the firing circuit of a recovered, but inert or rendered safe, IED for the purpose of demonstrating its viability as a functional device. A mock IED is an IED manufactured based on a circuit diagram or a surrogate copied from an IED recovered in situ, but without an initiator or explosives. In comparison, an inert IED is an IED recovered in situ, e.g., from the field, wherein the explosive components have been removed, but the fusing and firing system is intact and functional, less the initiator.
In addition to the need for safe energetic witness substitutes by the bomb technician community, the intelligence community, which is often challenged with analyzing IED schematic diagrams and IEDs recovered overseas, has a need for such safe alternatives. There is a constant flow of new IEDs and the U.S. Government needs to know if these devices will function as designed and thus, whether they are potential threats to national security. Bench-top and field testing of recovered IEDs is vital to address needs of the intelligence community.
The goal when defeating an IED is to prevent or mitigate its physical or chemical effect(s) while neutralizing the adversary's ability to exploit the value of the effect(s) in terms of building a platform to generate fear, terror, or propaganda. Countering an IED using defeat actions begins once the device has been emplaced and includes rendering it safe and conducting a thorough forensics analysis. Information derived from the physical exploitation of an IED and the analysis of how it was employed can be used as a basis for a variety of initiatives, including the development of technologies to detect and/or neutralize such devices and, ultimately, protect individuals.